This invention is in the field of active Fiber-Optic (FO) components and specifically in the field of FO matrix switch. This disclosure of my invention describes methods of implementing several functions in FO systems without any moving parts. These functions include, for example, N×N matrix switching with variable coupling, variable strength multiple port coupling, electronically variable attenuation, frequency shifting, and wavelength selection. All FO systems and networks encompassing telecommunication, data-communication, remote sensing, etc. utilize switching and other above-mentioned functions. My invention could be easily incorporate in those FO systems and would enhance system performance. The invention disclosed here falls into the specific category of high speed, high isolation, no moving parts phased array Acousto-Optic (AO) FO matrix switches.
Electro-mechanical movement of reflective or refractive elements commonly performs switching functions in FO systems and networks. Electro-mechanical movement is characterized by slow response time and low reliability. Recent advances with MicroElectroMechanical Systems (MEMs) based FO matrix switches (see articles by Daniel C. McCarthy and L. Y. Lin et al.) have improved speed and made MEMs switches the most widely used in the market, but speed is still in the millisecond range. Many FO systems and networks, such as packet switched voice and video traffic on Internet, require switching speed in the microsecond or sub-microsecond range. Electro-mechanical FO switches, even with MEMs technology, cannot operate in the microsecond range. The invention disclosed here would allow FO switches to operate at high speed (in sub-microsecond range) with high isolation and without moving parts. The FO switch scheme disclosed here is based on deflection of light by an AO deflector having one or more phased array transducers. This innovative FO switch will improve the performance and lower the cost of FO systems and networks.
Nabeel Riza in U.S. Pat. No. 6,282,336 B1 has disclosed a 2×2 FO switch using AO deflection. Several other attempts were made to realize FO switch using AO technology as listed in the said Riza's patent (also see article by Huang, P. C.). Earlier patents on 2×2 FO matrix switch that utilized a single AO deflector with zero and first-order deflected beams did not address inadequate (<50 dB) isolation problem. In other instances FO matrix switches required more than one AO deflectors and did not provide low insertion-loss. Two AO deflectors and an additional component such as a Dove Prism are used in Riza's patent to improve the isolation and realize low-insertion loss. However, the extra deflector and Dove prism add cost and increase the complexity of such a FO switch. The cost and complexity of Riza's 2×2 FO switch is expected to limit its use in general. My invention discloses high (>50 dB) isolation 2×2 FO switch using a single AO deflector without any additional optical element such as a Dove Prism. My invention will allow substitution of a common optical element (lens) for an array of individual collimating or GRIN lens at the input and output ends of fibers, further simplifying the construction of the switch.
U.S. Pat. No. 6,236,479 B1 by Gosseline et al. discloses an N×N FO matrix switch using two multi-channel AO deflectors. The said patent also contains description and mentions disadvantages such as high optical insertion loss, cross-talk and complexity of prior art N×N FO matrix switch schemes. Intend of my invention is to achieve similar FO switching function and performance as possible using schemes disclosed by Riza and Gosseline et al. in their respective patent but with only one AO deflector. An AO deflector with N phased array transducers as disclosed here can theoretically direct nearly 100% optical power from any input fiber to any output fiber. That makes a larger N×N FO matrix switch possible without any increase in the insertion loss or complexity.
As with many AO based FO switches, my invention can be used for high-resolution electronically variable optical attenuation, Wavelength Division Multiplexing (WDM), and other functions well known in the art of FO.